1. Field of the Invention
The present invention relates to an electric motor drive control device, and to an electrically driven power steering device, an electrically driven brake device, and an electrically driven pump device that employ such an electric motor drive control device.
2. Description of Related Art
Generally an electric motor drive device for controlling the driving of an electric motor includes a power conversion device that receives DC power from a DC power supply and generates AC power, and a control device for controlling this power conversion device. The AC power that is obtained from the power conversion device is supplied to the electric motor (that, for example, may be a synchronous three phase electric motor), and the electric motor generates rotational torque according to this AC power that is supplied thereto.
This type of electric motor drive device may be employed, for example for controlling the driving of an electric motor of some type that is mounted to an automobile. As one example of this, an electric motor drive device that is used to drive an electric motor in an electrically driven power steering device that supplements steering action for the automobile, or that powers one or more vehicle wheels in order to propel the automobile, or the like, may be arranged to drive control such a system device by converting DC power received from a secondary battery mounted to the automobile into AC power and by supplying this AC power to the corresponding electric motor. Since these applications are per se well known, further explanation thereof will herein be omitted.
With an electric motor drive device of the type described above, if an anomaly occurs upon one of the output lines, including both the wiring from the switching elements of the power conversion device to the electric motor and also the windings of the electric motor, then it is desirable to detect this anomaly in an appropriate manner, and to stop the operation of the electric motor and of the power conversion device safely. In order to satisfy this type of requirement, in Japanese Laid Open Patent Publication No. 2013-247754 described below, a technique is described for detecting an anomaly such as a ground fault or the like upon an output line by detecting the neutral point voltage of the electric motor, and by comparing this detected neutral point voltage with a predetermined threshold value.